The role of the homeobox gene Prox 1 in the regulation of mouse gamma-crystallin genes was investigated in collaboration with Dr. J. Graw (Institute of Mammalian Genetics, Neuherberg, Germany). It was shown that Prox 1 is able to stimulate the activity of the Crygf promoter 10-fold in vitro. It has been demonstrated (in collaboration with Dr. J. Wilting, Freiburg, Germany) that Prox 1 is a good marker for the developing lymphatic system in chickens and for the adult lymphatic system in normal tissues and cancers.